Downhole wireline tension measurement

ABSTRACT

A downhole string and method of operating where tension in the downhole string is monitored real time so that the tension in the downhole string does not exceed its yield strength. Included with the string is a tension sub for monitoring the tension that includes a sensor in the housing of the tension sub. The sensor can be a strain gauge and can be placed proximate an upper end of the downhole string so that tension in a wireline attached to the string can also be monitored. The portion of the housing having the sensor is narrowed for enhancing sensitivity of monitoring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/859,473, filed Jul. 29, 2013, the full disclosure of which is hereby incorporated by reference herein for all purposes.

BACKGROUND

1. Field of Invention

This invention relates in general to production of hydrocarbon from a subterranean wellbore, and in particular to a tension measurement device on a wireline.

2. Description of Prior Art

Some wellbore operations downhole involve deploying a downhole tool on a wireline, or other conveyance means. Typical downhole tools include perforating guns, logging tools, mechanical devices and downhole sensors. Logging tools generally measure the formation properties surrounding the wellbore, and often employ nuclear magnetic resonance devices or radioactive sources. Acoustic, radioactive, temperature, mechanical, electrical, dielectric, salintysensors are also sometimes used for measuring formation properties, but also have application for interrogating wellbore completion efforts, such as assessing integrity of cement that adheres casing to a wellbore wall.

Wireline is generally weaker than tubing or drill pipe, and susceptible to tensile separation tangling or snagging in a wellbore. Moreover, deeper wellbores pose additional difficulty as the wireline can stretch under its own weight, thereby further limiting the amount of tension that can be exerted onto the wireline from the downhole tool. Accordingly, care must be taken when deploying downhole tools on wireline so that tension applied to the wireline does not exceed its yield strength. Further, components of a downhole string, such as the cable head, connector subs in the string, or other elements of the string, can also be damaged if applied tension exceeds their yield strength.

SUMMARY OF THE INVENTION

Disclosed herein are examples of a tension sub and method for controlling tension in a conveyance means used for deploying a downhole tool string. An example of a tension sub for use in a downhole string includes a housing, a box end on an end of the housing that is coupled to a wireline, a pin end on an end of the housing that is distal from the box end and that is coupled to a downhole tool, and a sensor coupled with the housing that is responsive to tension in the housing. In this example, when the downhole tool string is deployed downhole and the wireline is put into tension, the tension is transmitted to the housing and sensed by the sensor. In one example the sensor is a strain gage, yet further optionally, the sensor is disposed on a reduced diameter portion of the housing. Electronics may optionally be provided in the housing for communicating what is sensed by the sensor to surface so that tension in the wireline can be monitored real time. The tension sub can include a switch for selectively providing communication between the sensor and surface and the downhole tool and surface. This example further includes electronics that are in a communication path between the sensor and the switch. Communication with surface and the downhole tool can be through the housing. In an embodiment, an upper end of the housing connects to a cable head, wherein the cable head attaches to the wireline.

Another example of a tension sub for use in a downhole string includes a housing having a box end that couples with a conveyance means for conveying the downhole string in a wellbore and a pin end that couples with a downhole tool, and a sensor engaged with the housing and that selectively communicates a signal to the surface that corresponds to a tension in the housing that is sensed by the sensor. Electronics may be included in the housing for communicating the signal to the surface. The tension in the housing can be dependent on a tension in the conveyance means. The conveyance means may be a wireline, coiled tubing, a slickline, or combinations thereof. In this example the sensor can be a strain gauge and placed on a portion of the housing having a reduced outer periphery.

An example of a method of downhole operations includes providing a tension sub having a housing, a box end, a pin end opposite the box end, and a sensor coupled with the housing, coupling the box end with a wireline and coupling the pin end to a downhole tool to define a downhole string, deploying the downhole string in a wellbore, and monitoring tension in the housing with the sensor and estimating tension in the wireline based on the tension monitored in the housing. An amount of tension exerted onto the wireline can be adjusted based on the step of monitoring tension in the housing. Adjusting an amount of tension exerted onto the wireline can include controlling pressure in the wellbore by pressurizing fluid and pumping the fluid into the wellbore. Alternatively, adjusting an amount of tension exerted onto the wireline may involve controlling a pulling force exerted onto the wireline at surface.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of an example of a downhole tool string on a wireline and having a tension sub in accordance with the present invention.

FIG. 2 is an elevational view of an example of a tension sub of FIG. 1.

FIG. 3 is a schematic example of components in the tension sub of FIG. 2.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term about includes +/−5% of the cited magnitude.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.

FIG. 1 illustrates in a side sectional view one example of a tool string 10 disposed in a deviated portion of a wellbore 12. The wellbore 12 is shown formed in formation 14. The tool string 10 is deployed on a wireline 16 shown extending into the wellbore 12 from a wellhead assembly 18 provided above an opening to the wellbore 12 and on surface 20. An optional surface truck 22 is also shown on surface 22 adjacent wellhead assembly 18 and connected to an upper terminal end of wireline 16. A cable head 24 on an upper end of the tool string 10 provides connectivity between the tool string 10 and the wireline 16. Connectivity includes mechanical connection to the wireline 16 so that the tool string 10 can be inserted into and drawn upward from within the wellbore 12. Connectivity through the cable head 24 also includes communication means, so that electricity, signals, data, and any other communication can be transmitted between the tool string 10 and wireline 16, and thus from tool string 10 to surface 20. In the tool string 10 next to the cable head 24 is a tension sub 26 for measuring tension, which thereby provides an indication of tension in the wireline 16 proximate the cable head 24. Moreover, the tension sub 26 is able to measure tension along a lower terminal end of wireline 16. A downhole tool 28 is shown connected to an end of tension sub 26 opposite its connection to cable head 24. Examples of the downhole tool 28 include perforating guns, logging tools, and any other tool that can be deployed downhole.

An example of the tension sub 26 is shown in an elevational view in FIG. 2, where the tension sub 26 includes an outer housing 30 for covering and protecting components internal to the sub 26. A box end 32 is shown an upper end of the tension sub 26 and that provides connection to the cable head 24 (FIG. 1) for communication between the downhole tool 28 and wireline 16. An electronics section 34 is included in this embodiment that includes electronics, such as the schematically illustrated printed circuit board 36. Electronics section 34 is adjacent the box end 32 on a side opposite the cable head 24 (FIG. 1). In an example, the electronics provides communication and control functionality for the tension sub 26. A sensor section 32 is shown in the tension sub 26 on a side of the electronics section 34 opposite the box end 32, and which includes a sensor 39 for measuring tension in the wireline 16 (FIG. 1). In the illustrated embodiment, sensor 39 is shown as a strain gauge 40 that couples with housing 30. In this example, strain gauge 40 senses strain in the housing 30, and thus tension in the string 10 and wireline 16. The sensor 39 may optionally be positioned along a neck portion 42 of the housing 41 shown having a reduced diameter. Positioning sensor 39 along the reduced diameter of the housing provides sensitivity to the measurements taken by the sensor 39. Examples exist wherein multiple sensors 39 are provided. Optionally, the sensor 39 can be situated in parts of the sensor section 38 away from the neck portion 42. Yet further optionally is the inclusion of a protective sleeve (not shown) to prevent the sensor 39 from breaking when torque is applied during rig up operations. The sleeve also has a provision for attaching slip over weight bars that are commonly used in pump-down operations.

A pin end 44 is shown on an end of the sensor section 38 opposite its connection to the electronics section 34, and on an end of the sub opposite the box end 32. A connector pin 46 is shown axially projecting from the pin end 44 for providing electrical and signal connectivity through the tension sub 26 so the rest of the tool string 10 (FIG. 1) can be in communication with the cable head 24 and wireline 16.

In one example where the sensor 39 is a strain gauge 40, electronics in the electronics section 34 selectively measure resistance of the strain gauge 40, where measured values of the resistance can reflect tension in the strain gauge 40, and thus tension in the wireline cable 16. Additional electronics may be included (not shown) that transmit signals representing the measurements recorded in the strain gauge 40, where the transmitted signals can be sent to surface 20 via the wireline 16 real time. In one example, included is a means to protect the mechanical sensor from damage from bending during lifting of the tool string prior to entering the well bore. The example means is a protective sleeve (not shown), which also provides a connection point for additional weight bars that slip over the wireline cable typically used in pump down operations.

FIG. 3 schematically illustrates example connectivity between sensor 39, electronics 36, and a switch 52 in the tension sub 26. As shown, communication link 48 provides communication between sensor 39 and electronics 36, communication link 54 provides communication from switch 52 to downhole tool 28, and communication link 56 provides communication from switch 52 to cable head 24. Switch 52 can thus selectively provide communication between sensor 39 (via electronics 36) and cable head 24, thereby communicating sensor 39 with surface 20 via wireline 16. In this example, when the tension sub 26 is active and tension measurements are being taken by tension sub 26, the switch 52 can selectively terminate communication to the tool string 10 via communication link 54 and to below the tension sub 26. In another example of operation, when the downhole tool 28 is in position for perforating, logging, or other downhole operations, the switch 52 can cease communication between electronics 36 and switch 52 through communication link 50, thereby isolating sensor 39 from communication with surface 20. Thus in this example, tension measurements are interrupted while the downhole tool 28 is in operation. Examples of the communication links 48, 50, 54, 56 include electrical wiring, fiber optics, wireless signals, and combinations thereof. The wireless signals can be any type of waves, such as radio, ultraviolet, microwaves, acoustic, and the like.

In an example, fluid (not shown) is pressurized with a pressure source 58 and then pumped into the wellbore 12 for urging the tool string 10 deeper into the wellbore 12 (FIG. 1). Applying an urging force to the tool string 10 is sometimes required when the tool string 10 is in a horizontal or deviated portion of the wellbore 12 as shown. In some situations, the fluid can exert a tensile force in the tool string 10, which is transmitted to the wireline 16, where the tensile force exceeds the yield strength of one or more of the wireline 16, cable head 24, or any element of the tool string 10, thereby creating a disconnection, separation, and/or fracture in one or more of the wireline 16, cable head 24, or tool string 10. A fishing job is typically required to retrieve the tool string 10 from the wellbore 12 if all or a portion of the tool string 10 becomes separated from the wireline 16. Real time measurement of tension in the tool string 10 and proximate the cable head 24, as provided by the tension sub 26 as described above; can optimize pump down operations of the tool string 10. For example, because of the difficulties in modeling downhole conditions due to changing fluid densities, changes in deviation of the wellbore 12, and elongation of the wireline 16, a designated operational pressure may be insufficient to complete the operation. Insufficient pressure in the wellbore 12 to due to the difficulties listed above, the tool string 10 may become stuck in the wellbore 12, or not progress through the wellbore 12 at a high enough rate. Alternatively, modeling may result in pumping at too high a pressure, thereby risking downhole failure of the wireline 16, tool string 10, or cable head 24. Instead, real time monitoring of tensile force at, or safely below, the expected region of possible failure allows an operator to pump fluid at a pressure so the tool string 10 moves at or close to a maximum rate without the risk of separating the tool string 10 from the wireline 16. Moreover, by knowing the tensile force in the tool string 10, the operator can make adjustments to not only fluid pressure, but also to flow rate and/or fluid properties, such as density and speed of the wireline 16. Optionally, an amount of pulling force can be controlled that is exerted onto the wireline 16 from a reel (not shown) associated with the surface truck 22; where the amount of control on the force is regulated based on the tension monitored in the housing 20 (FIG. 2) and thus the wireline 16.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, instead of wireline 16, coiled tubing or slickline can be used as a conveyance means for deploying the downhole string 10 within the wellbore 12. Moreover, as embodiments of the disclosed tension sub are sufficiently robust, the associated downhole string 10 can be run with explosive devices including plugs, packers, severing tools and perforating guns. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. 

What is claimed is:
 1. A tension sub for use in a downhole string comprising: a housing; a box end on an end of the housing that is coupled to a wireline; a pin end on an end of the housing that is distal from the box end and that is coupled to a downhole tool; and a sensor coupled with the housing that is responsive to tension in the housing, so that when the downhole string is deployed downhole and the wireline is put into tension, the tension is transmitted to the housing and sensed by the sensor.
 2. The tension sub of claim 1, wherein the sensor comprises a strain gage.
 3. The tension sub of claim 1, wherein the sensor is disposed on a reduced diameter portion of the housing.
 4. The tension sub of claim 1, further comprising electronics in the housing for communicating what is sensed by the sensor to surface so that tension in the wireline can be monitored real time.
 5. The tension sub of claim 1, further comprising a switch for selectively providing communication between the sensor and surface and the downhole tool and surface.
 6. The tension sub of claim 5, further comprising electronics in a communication path between the sensor and the switch.
 7. The tension sub of claim 1, wherein communication with surface and the downhole tool is through the housing.
 8. The tension sub of claim 1, wherein an upper end of the housing connects to a cable head, wherein the cable head attaches to the wireline.
 9. A tension sub for use in a downhole string comprising: a housing having a box end that couples with a conveyance means for conveying the downhole string in a wellbore and a pin end that couples with a downhole tool; and a sensor engaged with the housing and that selectively communicates a signal to the surface that corresponds to a tension in the housing that is sensed by the sensor.
 10. The tension sub of claim 9, further comprising electronics in the housing for communicating the signal to the surface.
 11. The tension sub of claim 9, wherein the tension in the housing is dependent on a tension in the conveyance means.
 12. The tension sub of claim 9, wherein the conveyance means comprises an element selected from the group consisting of a wireline, coiled tubing, a slickline, and combinations thereof.
 13. The tension sub of claim 9, wherein the sensor comprises a strain gauge and wherein the strain gauge is placed on a portion of the housing having a reduced outer periphery.
 14. A method of downhole operations comprising: providing a tension sub having a housing, a box end, a pin end opposite the box end, and a sensor coupled with the housing; coupling the box end with a wireline and coupling the pin end to a downhole tool to define a downhole string; deploying the downhole string in a wellbore; and monitoring tension in the housing with the sensor and estimating tension in the wireline based on the tension monitored in the housing.
 15. The method of claim 14, further comprising adjusting an amount of tension exerted onto the wireline based on the step of monitoring tension in the housing.
 16. The method of claim 15, wherein the step of adjusting an amount of tension exerted onto the wireline comprises controlling pressure in the wellbore by pressurizing fluid and pumping the fluid into the wellbore.
 17. The method of claim 15, wherein the step of adjusting an amount of tension exerted onto the wireline comprises controlling a pulling force exerted onto the wireline at surface. 